dash temp gauge issue... I'm stumped.

51f1truck

51f1truck

Junior Member
My 52 Ford F-1 with the 239 ci V8 flathead ... new radiator, pumps, engine cooked cleaned, new 180 deg F thermostats. I have a mechanical temp gauge that I have swapped to both heads. The mech temp gauge runs very steady at 180 degrees so I feel good about how the flathead is running.

My problem is my dash gauge reads very near "H" while driving. Now as we all know, when the ignition is off, the temp gauge goes to "H". When I first start it, the gauge works like expected and drops to Cold and then starts to move up as I drive. The problem is that when I am running at 180 deg normal operating temp, the gauge reads very near "H".

I tried wiring it with and without the double terminal excessive heat switch, no difference. I purchased a replacement single terminal temp sender, no difference. I installed a second dash temp gauge that I have, same readings near "H" while driving.

I am stumped. I don't understand why the dash temp gauge read so close to "H" when driving at normal temps. I don't want to install aftermarket gauges in the cab as I think this will take away some of the "stock" look I have been working on.

Any ideas on what else to check... or is this typical ?

Fred
 
sounds like the sending unit on the block is at failt. there are two as you know so one or both is on the fritz
 
That is exactly what I thought... so I shelled out $50 for a new sender.

For now, I only have the single terminal sender connected, and it is a new sender. I got the same readings with my original sender and with this replacement sender.

(I don't have the double terminal excessive heat switch installed right now. I am using that port for my mechanical temp gauge.)

Fred
 
The dash units are calibrated and the sender for 150-160 T Stats at 180 it will read on the H I know i have been down the same road with mine.
 
Last edited:
51f1truck said:
That is exactly what I thought... so I shelled out $50 for a new sender.

For now, I only have the single terminal sender connected, and it is a new sender. I got the same readings with my original sender and with this replacement sender.

(I don't have the double terminal excessive heat switch installed right now. I am using that port for my mechanical temp gauge.)

Fred
Click to expand...

When you removed the double sender did you connect those two wires together? if not, tie them together with a small screw and tape them so they don't short out. now the single unit should work..jdl
 
That is very common. The old temp gauges tend to drift up as they age. My '40 runs up near the H but is only about 185.
 
It is pretty typical of the the system. Mine indicates high normal at 170°- 180°. I tweaked the gauge to read that. It originally read very close to hot after warm up. My quick cal is: Unpowered, set the pointer to indicate hot at the "H" (Zero point). Powered with 5.5-6.0 volts set the pointer so it shows slightly below cold (full scale/span point). I used 4 AA batteries to do this. You will need to take the guage out of the panel and remove the mounting plate to make the adjustment. There are 2 holes in the back of the gauge with what looks like gear teeth. They are the adjustments. The lower left adjustment hole is the zero point. The upper right adjustment hole is the full scale/span point.
 
I remember a year or so ago some had a thread on how to adjust the temp gauge by using diodes or something to adjust current so you could make gauge read what you wanted.It had something to do with the wiring?Maybe some one can explain!
 
With the wire from the gauge to the sending unit removed and insulated from ground the gauge should not move or function, if it does the insulated wire may be grounded. If you only have one port to use for the sending units, install the single terminal unit only. If the gauge then reads high, when the engine is warm and seems to function properly otherwise, the sending unit is not working properly for your gauge.
 
51,
I just went thru the same issue. I grabbed all my sending units
and a known good dash gage and using an old Coleman stove and
a pan of water and Alices meat thermometer I tested each sending unit.
I tested 10 sending units ,4 were close 2 were way high the rest were
right on the money. Yep I used a regular 6 volt battery as a power
source. Real shade tree huh !
Charlie ny
 
You must log in or register to reply here.
Back
Top